1. Field of the Invention
The present invention relates to a pressure damper for reducing pressure fluctuations of fluid, and more particularly, to a pressure damper having a function of converting pressure fluctuations of fluid into an electrical signal, and a liquid jet head and a liquid jet apparatus using the same.
2. Description of the Related Art
In recent years, there has been used an ink jet type liquid jet head for discharging ink droplets on recording paper or the like to print a character or graphics on the recording paper or for discharging a liquid material on a surface of an element substrate to form a functional thin film. In such a liquid jet head, ink or a liquid material is supplied from a liquid tank via a supply tube to the liquid jet head, and the ink or the liquid material filled into a channel is discharged from a nozzle which communicates to the channel. When the ink is discharged, the liquid jet head or a recording medium on which jetted liquid is to be recorded is moved to print the character or the graphics on the recording paper, or, to form a functional thin film in a predetermined shape. In this kind of device, it is necessary to control with high precision the amount of a liquid droplet discharged from a nozzle and a discharge speed. Therefore, it is necessary to control with high precision the pressure of ink in a discharge plane of the nozzle.
For example, Japanese Patent Application Laid-open No. 2005-231351 describes an ink jet recording apparatus including a regulating structure of the pressure of liquid which is discharged from a print head. The ink jet recording apparatus includes a main tank for storing ink, a sub-tank for receiving ink supply from the main tank and supplying the ink to an ink jet head, a pump for regulating an internal pressure of the sub-tank, and a pressure gauge placed for ink supply. In the ink jet recording apparatus, by regulating the internal pressure of the sub-tank according to status of usage, an internal pressure of ink is controlled. For example, when highly viscous ink is discharged, or auxiliary discharge is used for letting out air bubbles, negative pressure on ink is controlled to be lower than that when printing is carried out.
However, in the ink jet recording apparatus described in Japanese Patent Application Laid-open No. 2005-231351, the pressure gage is connected to a tube which is branched from a part of a liquid supply path. Thus, liquid which passes through the liquid supply path may enter the pressure gage side. The liquid jet head reciprocates at high speed. In particular, when the direction of movement of the liquid jet head is reversed or when the liquid jet head undergoes rapid acceleration, due to inertia of liquid in a tube, the internal pressure fluctuates. The pressure fluctuations cause liquid to enter the pressure gauge, which in turn causes ink or liquid which enters the pressure gauge to thicken or solidify to lower detection precision of the pressure gauge. As a result, there are problems that, for example, pressure control of the ink or the liquid material becomes inadequate to thereby lower the recording quality.